1. Field of the Invention
The present invention relates to an imaging device and a shading correction method capable of reliably correcting shading due to pupil division, and capable of easily obtaining a three-dimensional image with a small shading difference compared with a two-dimensional image.
2. Description of the Related Art
JP-A-10-42314 discloses an imaging device that obtains a three-dimensional image using a pupil division method. In an imaging element of the imaging device, an object is imaged by the imaging element while changing the size of a pupil of an imaging lens by an optical shutter to obtain plural viewpoint images.
JP-A-2008-299184 discloses a focus detection apparatus that performs focus detection using a pupil division phase difference detection method. The focus detection apparatus includes an imaging element in which pixels are arranged in two-dimensions and an optical axis of a microlens and the center of a pixel (photoelectric conversion element) are shifted. Here, a configuration in which addition is performed between pixels in which a pupil is shifted to smoothen a blurred image in a non-focused state is disclosed.
JP-A-2009-244858 discloses an imaging device capable of performing focus detection using a pupil division phase difference detection method. Here, a configuration in which three types of shading corrections for a normal pixel, an A image of a focus detection pixel and a B image thereof are performed is disclosed.
JP-A-2011-17800 discloses an imaging device capable of performing focus detection using a pupil division phase difference detection method. Here, a configuration in which pixel values of two pixels in the same pixel group are averaged to enhance the signal-to-noise ratio is disclosed.
However, according to the findings of the present inventors, in the imaging device that obtains the three-dimensional image using the pupil division method as disclosed in JP-A-10-42314, an incident angle of object light is controlled in a laterally opposite direction to allow three-dimensional imaging, and in the case of a lens in which a main ray angle from the lens is changed at an image forming position, shadings with extremely different characteristics occur in a right viewpoint image and a left viewpoint image.
Further, according to the finding of the present inventors, both of imaging of a three-dimensional image (three-dimensional imaging) and imaging of a two-dimensional image (two-dimensional imaging) can be performed with high image quality by reducing the shading difference between the three-dimensional image and the two-dimensional image.